More than two hundred and fifty years have elapsed since George Berkeley first published his Principles of Human Knowledge and thereby divided the intelligible world into “notions” and “ideas". In the ensuing period, the more articulate world has shown a marked preference for treating only his theory of “ideas” .The result has been misleading. It is therefore the purpose of this essay to present Berkeley' s theory of “notions”, in so far as it can be gleaned from the pages of (...) his extant works, and to emphasize the importance of "notions" in any fair-minded attempt to view Berkeleyan philosophy as a whole. The vital role of a theory of notions will become evident in due course. (shrink)